System-Level Characterization of High-Speed Silicon Photonics Travelling Wave Mach-Zehnder Modulators

Abstract

We present a comprehensive system-level characterization of silicon photonics (SiP) C-band and O-band traveling-wave Mach–Zehnder modulators (TWMZMs) implemented using imec silicon photonics process design kit (PDK). This work focuses on evaluating the performance limits and application suitability of these TWMZMs for high-speed optical interconnects. Using the C-band TWMZM, we demonstrate optical amplification-free transmission of 256 Gbaud (net 241 Gb/s) on-off keying (OOK), 150 Gbaud (net 291 Gb/s) pulse amplitude modulation with 4 levels (PAM4), 128 Gbaud (net 301 Gb/s) PAM6, and 95 Gbaud (net 268 Gb/s) PAM8 signals over 100 meters of standard single-mode fiber (SMF), achieving a 6.25% overhead hard decision-forward error correction (HD-FEC) threshold. With optical amplification, the same modulator supports data rates of 175 Gbaud (net 329 Gb/s) PAM4, 145 Gbaud (net 341 Gb/s) PAM6, and 112 Gbaud (net 316 Gb/s) PAM8. For the O-band TWMZM, we achieve rates up to 224 Gbaud (net 210 Gb/s) OOK and 140 Gbaud (net 263 Gb/s) PAM4 transmission over 500 meters of SMF. We perform detailed analysis of both TWMZM performance in 200 Gb/s per lane scenarios as defined by the IEEE 802.3dj Task Force. Our results show that both modulators meet defined requirements with a simple 13-tap feed-forward equalizer (FFE). We also assess the thermal performance of the C-band TWMZM across multiple operating conditions. These results demonstrate the potential for high-performance, DR and FR-compliant 200 Gb/s per lane transceivers based on SiP TWMZMs with minimal DSP requirements, and mark significant progress toward enabling 400 Gb/s per lane transceivers using conventional SiP technologies.